For those of us that do not sync with Google, or as is my case, do not have any Google services or apps, the new messaging app is worse than the previous one.
The CM12 messaging app allowed all SMS/MMS to be exported as a zip file, that could be imported to another phone, or to the same phone after a clean wipe. The CM13 messaging app is missing this functionality, and I could not find another one that would replicate it.
Otherwise, CM13 is pretty solid. I've been running the nightlies since they came out on an LG G3 d852, which is a bit of a crappy phone, and it is much more stable than CM12. I do like the new camera app, as it has a lot more functionality than the old one, and the OS overall is a bit more polished.
YMMV, as it really depends on the hardware. I'm sure on a Nexus 5p or 6x, CM13 is stellar. On my frankenstein LG G3, it's ok, as I am forced to run a KK bootloader (only rootable bootloader), a LL modem (most recent modem released by the Canadian carriers) and a MM CM13 OS.